This section provides background information related to the present disclosure which is not necessarily prior art.
Traditionally, a PEPS system allows anyone in possession of a key fob that has been previously paired with a vehicle's central PEPS electronic control unit (ECU) to access the vehicle by simply grabbing the door handle and to start the vehicle with a push of a button. In response to a button push, the central PEPS ECU authenticates the key fob to determine if the key fob is authorized to access the vehicle and uses the signal strength indicated by a plurality of vehicle antennas to estimate the location of the Key Fob. If the Key Fob can be authenticated and is located within an authorizing zone, the vehicle's function is made available to the user (i.e. doors are unlocked or vehicle is started).
Traditional PEPS systems use proprietary grade radio protocols using low frequency (LF) signals of approximately 125 kHz. Traditional PEPS systems are also hampered by the physics of the LF systems. LF was selected by early PEPS systems because the wave propagation allows for relatively accurate estimation of range and location by using signal strength within the typical target activation range of 2 meters. However, due to the extremely long wavelength of the LF signal compared to the size of a practical vehicle antenna and key fob receiver, it is difficult within reasonable power consumption and safe transmit power levels to reliably communicate with a key fob using LF beyond a few meters.